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Layered Stack Configuration

Atmos Design Pattern

The Layered Stack Configuration Design Pattern describes the mechanism of grouping Atmos components by category or function, adding the groups of components to layers, and importing the layers into top-level Atmos stacks.

Each layer imports or configures a set of related Atmos components. Each Atmos component belongs to just one layer. Each layer can be managed separately, possibly by different teams.

note

The Layered Stack Configuration Design Pattern works around the limitations of the Partial Stack Configuration pattern. Instead of splitting the top-level Atmos stacks into parts, the Layered Stack Configuration pattern adds separate layers to group the related Atmos components by category, and then import the layer manifests into the top-level Atmos stacks.

Use-cases​

Use the Layered Stack Configuration pattern when:

  • You have many Atmos components, and you need to group the components by category or function

  • You want to split the components into layers. Each layer should be managed and modified independent of the other layers, possibly by different people or teams

  • You want to keep the configuration easy to manage and DRY

Benefits​

The Layered Stack Configuration pattern provides the following benefits:

  • Allows to group Atmos components by category or function

    people or teams. Furthermore, controls like GitHub's CODEOWNERS can be leveraged so that specific teams or individuals must review changes to these files.

  • Allows importing only the required layers into the top-level stacks (only the groups of components that need to be provisioned in the stacks)

  • Makes the configurations easier to understand

Example​

In the following structure, we have various Terraform components (Terraform root modules) in the components/terraform folder.

In the stacks/catalog folder, we define the defaults for each component using the Component Catalog Atmos Design Pattern.

In the stacks/layers folder, we define layers (groups of components), and import the related components into the layer manifests:

  • load-balancers.yaml
  • data.yaml
  • dns.yaml
  • logs.yaml
  • notifications.yaml
  • firewalls.yaml
  • networking.yaml
  • eks.yaml
   │   # Centralized stacks configuration (stack manifests)
   ├── stacks
   │   ├── catalog  # component-specific defaults
   │   │   ├── alb
   │   │   │   └── defaults.yaml
   │   │   ├── aurora-postgres
   │   │   │   └── defaults.yaml
   │   │   ├── dns
   │   │   │   └── defaults.yaml
   │   │   ├── eks
   │   │   │   └── defaults.yaml
   │   │   ├── efs
   │   │   │   └── defaults.yaml
   │   │   ├── msk
   │   │   │   └── defaults.yaml
   │   │   ├── ses
   │   │   │   └── defaults.yaml
   │   │   ├── sns-topic
   │   │   │   └── defaults.yaml
   │   │   ├── network-firewall
   │   │   │   └── defaults.yaml
   │   │   ├── network-firewall-logs-bucket
   │   │   │   └── defaults.yaml
   │   │   ├── waf
   │   │   │   └── defaults.yaml
   │   │   ├── vpc
   │   │   │   └── defaults.yaml
   │   │   └── vpc-flow-logs-bucket
   │   │       └── defaults.yaml
   │   ├── layers  # grouping of components by category/function
   │   │   ├── load-balancers.yaml
   │   │   ├── data.yaml
   │   │   ├── dns.yaml
   │   │   ├── logs.yaml
   │   │   ├── notifications.yaml
   │   │   ├── firewalls.yaml
   │   │   ├── networking.yaml
   │   │   └── eks.yaml
   │   ├── mixins
   │   │   ├── tenant  # tenant-specific defaults
   │   │   │   └── plat.yaml
   │   │   ├── region  # region-specific defaults
   │   │   │   ├── us-east-2.yaml
   │   │   │   └── us-west-2.yaml
   │   │   └── stage  # stage-specific defaults
   │   │       ├── dev.yaml
   │   │       ├── staging.yaml
   │   │       └── prod.yaml
   │   └── orgs  # Organizations
   │       └── acme
   │           ├── _defaults.yaml
   │           └── plat  # 'plat' represents the "Platform" OU (a.k.a tenant)
   │               ├── _defaults.yaml
   │               ├── dev
   │               │   ├── _defaults.yaml
   │               │   ├── global-region.yaml
   │               │   ├── us-east-2.yaml
   │               │   └── us-west-2.yaml
   │               ├── staging
   │               │   ├── _defaults.yaml
   │               │   ├── global-region.yaml
   │               │   ├── us-east-2.yaml
   │               │   └── us-west-2.yaml
   │               └── prod
   │                   ├── _defaults.yaml
   │                   ├── global-region.yaml
   │                   ├── us-east-2.yaml
   │                   └── us-west-2.yaml
   │   # Centralized components configuration
   └── components
       └── terraform  # Terraform components (a.k.a Terraform "root" modules)
           ├── alb
           ├── aurora-postgres
           ├── dns
           ├── eks
           ├── efs
           ├── msk
           ├── ses
           ├── sns-topic
           ├── network-firewall
           ├── network-firewall-logs-bucket
           ├── waf
           ├── vpc
           └── vpc-flow-logs-bucket

Add the following minimal configuration to atmos.yaml CLI config file :

atmos.yaml
components:
  terraform:
    base_path: "components/terraform"

stacks:
  base_path: "stacks"
  name_pattern: "{tenant}-{environment}-{stage}"
  included_paths:
    # Tell Atmos to search for the top-level stack manifests in the `orgs` folder and its sub-folders
    - "orgs/**/*"
  excluded_paths:
    # Tell Atmos that the `defaults` folder and all sub-folders don't contain top-level stack manifests
    - "defaults/**/*"

schemas:
  jsonschema:
    base_path: "stacks/schemas/jsonschema"
  opa:
    base_path: "stacks/schemas/opa"
  atmos:
    manifest: "stacks/schemas/atmos/atmos-manifest/1.0/atmos-manifest.json"

Add the following configuration to the stacks/layers/load-balancers.yaml layer manifest:

stacks/layers/load-balancers.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/alb/defaults
  # Import other Load Balancer components

Add the following configuration to the stacks/layers/data.yaml layer manifest:

stacks/layers/data.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/aurora-postgres/defaults
  - catalog/msk/defaults
  - catalog/efs/defaults
  # Import other Data components

Add the following configuration to the stacks/layers/dns.yaml layer manifest:

stacks/layers/dns.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/dns/defaults
  # Import other DNS components

Add the following configuration to the stacks/layers/logs.yaml layer manifest:

stacks/layers/logs.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/network-firewall-logs-bucket/defaults
  - catalog/vpc-flow-logs-bucket/defaults
  # Import other Logs components

Add the following configuration to the stacks/layers/notifications.yaml layer manifest:

stacks/layers/notifications.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/ses/defaults
  - catalog/sns-topic/defaults
  # Import other Notification components

Add the following configuration to the stacks/layers/firewalls.yaml layer manifest:

stacks/layers/firewalls.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/network-firewall/defaults
  - catalog/waf/defaults
  # Import other Firewall components

Add the following configuration to the stacks/layers/networking.yaml layer manifest:

stacks/layers/networking.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/vpc/defaults
  # Import other Networking components

Add the following configuration to the stacks/layers/eks.yaml layer manifest:

stacks/layers/eks.yaml
import:
  # Import the related component manifests into this layer manifest
  - catalog/eks/defaults

Import the required layers into the stacks/orgs/acme/plat/dev/us-east-2.yaml top-level stack manifest:

stacks/orgs/acme/plat/dev/us-east-2.yaml
import:
  # The `orgs/acme/plat/dev/_defaults` and `mixins/region/us-east-2` manifests
  # define the top-level Atmos stack `plat-ue2-dev`
  - orgs/acme/plat/dev/_defaults
  - mixins/region/us-east-2
  # Import the layers (groups of components)
  - layers/load-balancers
  - layers/data
  - layers/dns
  - layers/logs
  - layers/notifications
  - layers/firewalls
  - layers/networking
  - layers/eks

Import the required layers into the stacks/orgs/acme/plat/dev/us-west-2.yaml top-level stack manifest:

stacks/orgs/acme/plat/dev/us-west-2.yaml
import:
  # The `orgs/acme/plat/dev/_defaults` and `mixins/region/us-west-2` manifests
  # define the top-level Atmos stack `plat-uw2-dev`
  - orgs/acme/plat/dev/_defaults
  - mixins/region/us-west-2
  # Import the layers (groups of components)
  - layers/load-balancers
  - layers/data
  - layers/dns
  - layers/logs
  - layers/notifications
  - layers/firewalls
  - layers/networking
  - layers/eks

Import the required layers into the stacks/orgs/acme/plat/prod/us-east-2.yaml top-level stack manifest:

stacks/orgs/acme/plat/prod/us-east-2.yaml
import:
  # The `orgs/acme/plat/prod/_defaults` and `mixins/region/us-east-2` manifests
  # define the top-level Atmos stack `plat-ue2-prod`
  - orgs/acme/plat/prod/_defaults
  - mixins/region/us-east-2
  # Import the layers (groups of components)
  - layers/load-balancers
  - layers/data
  - layers/dns
  - layers/logs
  - layers/notifications
  - layers/firewalls
  - layers/networking
  - layers/eks

Similarly, import the required layers into the other top-level stacks for the other organizations, OUs/tenants, accounts and regions. Make sure to import only the layers that define the component that need to be provisioned in the stacks.

References​